Plate Boundaries-Divergent-Convergent-Transform - MooMooMath and Science (360p, h264, youtube)

Plate Boundaries

Overview

  • Dramatic changes in the Earth's crust occur along plate boundaries, including:

    • Formation of mountain ranges

    • Creation of new islands

    • Occurrence of earthquakes

  • There are three main types of plate boundaries:

    • Divergent Boundaries

    • Convergent Boundaries

    • Transform Boundaries

Convergent Boundaries

  • Occur when two tectonic plates collide.

Types of Convergent Boundaries:

  1. Continental to Continental

    • Two plates of continental crust collide.

    • Results in buckling and thickening of the crust, forming mountains.

  2. Continental to Oceanic

    • Ocean crust collides with continental crust.

    • Oceanic crust, being thicker, subducts under the continental crust.

    • Resultant magma from melted oceanic crust leads to the formation of volcanoes along the boundary.

  3. Ocean to Ocean

    • When two plates of oceanic crust collide.

    • The older, denser plate subducts under the younger plate.

    • This melting results in the creation of an island arc.

Divergent Boundaries

  • Occur when two plates move away from each other.

  • Separation allows the asthenosphere (soft layer of the mantle) to rise towards the surface and partially melt.

    • This melting creates magma that erupts as lava.

    • Lava cools and hardens to create new rock, forming new ocean floor or continental crust.

  • Formation of new lithosphere occurs as the upper part of the asthenosphere cools and becomes rigid.

    • Often found on the ocean floor, but can also create rift valleys when continents are separated.

Transform Boundaries

  • Occur where two plates move past each other horizontally.

  • The movement is not smooth; plates scrape against each other causing sudden slippages of crustal rock, which can be felt as earthquakes.

  • Unlike convergent and divergent boundaries, transform boundaries typically do not produce magma.

  • Example: San Andreas Fault in California is a major transform boundary.

Conclusion

  • Recap of the three types of plate boundaries:

    • Convergent

    • Divergent

    • Transform

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